Multiple layers of microwave transmission lines are commonly used to reduce the size of microwave circuits and improve their performance. Miniature microwave integrated circuit (MMIC) packaging commonly employs such multi-layer technology.
Interconnections between layers has conventionally been accomplished by direct contact, e.g., by feed-through pins extending between layers in plated through holes, and which pins are soldered to transmission line conductors in the layers. Such interconnections are relatively difficult and expensive to fabricate. Moreover, once the pins have been soldered in place, disassembly of the layers requires that the solder connections be broken or disassembled. This significantly increases the difficulty of trouble-shooting malfunctions or testing the assembly.
In an attempt to provide a multilayer assembly which can more readily be disassembled, interconnection between microwave circuits on different layers has been accomplished by press contact with a mini-bellows interconnect element extending between the layers. Such bellows elements are not soldered to the conductors, and therefore the layers may more readily be disassembled for repair or testing. If the contact surfaces of the bellows or the conductors to which the bellows make contact are dirty, the effectiveness of the interconnection will be impaired.